In the offshore technology, floating production, storage and offloading vessels, drilling rigs or barges, are often anchored to the seabed by means of catenary anchor lines or anchor chains. From a subsea structure, such as an oil well, flexible risers may be attached to the vessel or to the rig, for instance via a turret around which the vessel or rig can weathervane. In case of emergencies or high seas and strong winds, the known disconnect means can be actuated by means of a radio signal from the vessel, acoustically or electrically through a cable connection, such that for instance an hydraulic actuating mechanism detaches the first and second halves of the disconnect means. Rig anchor release units of the above type are for instance available from InterOcean systems inc, San Diego.
The known disconnect means have as a disadvantage that they are located relatively far below the water surface, such that they cannot be easily inspected for maintenance purposes. Furthermore, after disconnecting the parts of the disconnect means, the part that is attached to the vessel by an anchor line may cause problems in shallow waters or may interfere with risers around the drilling well or other objects on the sea bed.